385HP 454 Rod Knocking

[alldodge]

Re: 385HP 454 Rod Knocking

I believe (Not 100% sure) Mercruiser solved some of the problems with a lean condition going into cylinder number 7 by late 1998+. One problem they had with the 454/502 MPI's was the number 7 intake was not bored out enough to flow proper amount of fuel flow from the injector due to design. There are a few discussions about it on Offshoreonly that I see you're a forum member as well.

Do a search of "MPI #7 fuel rail defect???" and a few will pop up that you may want to at least know about.
Also this, 502 MPI - ASM lower intake versus stock
and there's one more good one over there about someone modifying the hole with photos, but for the life of me, I can not find it.:blue:

You said you had one cylinder that looked rich? Just curious which one? 6 or 8 by chance?

It is number 8, but as before not much just a little more then the rest.

From what I have noticed thus far, Some Merc remanufactured engines are not able to be identified by a Mercruiser dealer or online. The only way to have it identified would be by calling Mercruiser customer support in the U.S.

I'll give that a try, thaks
Info is
Bore .030
Mains .020
Thrust width STD
Rod .020
Mfg 7/29/2006
S/N 91003823

Start a new thread Just kidding. If all the engine sensors are working correctly and within range and the fuel PSI is normal and you have the correct spark plugs & your engine temp gets to 163 degrees, You should not be needing to do that for that reason.

You may want to do an injector balance test. You can find the procedure in the manual.

Also on Offshoreonly, search vst running rich.

Sure do appreicate the info will give it a try. Just picked up a new Merc Scantool with fitting for all Merc EFI's. Says it has Version 6 software, hope this will help figure some of my issues out.

 

[Fun Times]

Re: 385HP 454 Rod Knocking

S/N 91003823
Sure do appreicate the info will give it a try. Just picked up a new Merc Scantool with fitting for all Merc EFI's. Says it has Version 6 software, hope this will help figure some of my issues out.

Yep, That looks like a number I recall not being able to find without calling.

Good luck to you with getting your engine to run better, we're here if you need any advice.

 

[alldodge]

Re: 385HP 454 Rod Knocking

Update:
Call ed Merc customer service and they checked on the white silicone like stuff on the threads. They said that is thread sealing stuff which ensures or more correct torque. They do put it on Head and rocked bolts.

Merc said they have no idea of when an engine was rebuilt by their rebuilder (sure you don't) and cannot take the S/N and find out anything.

Plan to take the 7.4 to a shop and see if they can tell why it failed. Looks like the Starboard engine has 2 week cylinders (6 and 7), go figure. Plan to run it until it fails. Pt the scanner on it and only thing that showed up was IAC is high, but figure with the uneven idle it could be from low compression.